(1):

(n.) An agent between two parties; a broker; a go-between; any dealer between the producer and the consumer; in Ireland, one who takes land of the proprietors in large tracts, and then rents it out in small portions to the peasantry.

(2):

(n.) A person of intermediate rank; a commoner.

(3):

(n.) The man who occupies a central position in a file of soldiers.